docs: def bytealign(self):
          """Align to next byte and return number of skipped bits.
  
          Raises ValueError if the end of the bitstring is reached before
          aligning to the next byte.
  
          """
          skipped = (8 - (self._pos % 8)) % 8
          self.pos += self._offset + skipped
          assert self._assertsanity()
          return skipped